Table 3.
Comparison of case and control subjects with BRCA1 and BRCA2 mutationsa
| Variable | Case subjects (N = 1,694) | Control subjects (N = 1,694) | P value |
| Current age (mean) | 49.3 | 48.6 | 0.22 |
| Year of birth (mean year) | 1951.2 | 1951.8 | 0.10 |
| Mutation, N (%) | |||
| BRCA1 | 1,313 (77.5%) | 1,313 (77.5%) | |
| BRCA2 | 380 (22.4%) | 380 (22.4%) | |
| Country of residence, N (%) | |||
| United States | 591 (34.9%) | 591 (34.9%) | |
| Canada (excluding Quebec) | 491 (29.0%) | 491 (29.1%) | |
| Poland | 439 (25.9%) | 439 (25.9%) | |
| Israel | 102 (6.0%) | 102 (6.0%) | |
| Norway | 55 (3.2%) | 55 (3.2%) | |
| Sweden | 7 (0.4%) | 7 (0.4%) | |
| United Kingdom | 6 (0.4%) | 6 (0.4%) | |
| Austria | 1 (0.1%) | 1 (0.1%) | |
| Italy | 2 (0.1%) | 2 (0.1%) | |
| Parityb, mean | 2.2 | 2.2 | |
| Oophorectomy | 61 (3.6%) | 109 (6.4%) | 0.0002 |
| Oral contraceptive use, N (%) | |||
| Ever | 1,002 (59.8%) | 1,009 (60.1%) | 0.89 |
| Age at menarche, mean | 12.9 | 13.0 | 0.001 |
aParity, miscarriages, and therapeutic abortions were censored one year prior to the breast cancer diagnosis of the case. Data for age at menarche, parity and therapeutic abortions are missing for a few study subjects. bParity includes live born and still born only, and was included in analysis only if birth was one calendar year before the age of diagnosis of the matched case.